This proposal describes experiments intended to examine the effects of calcium, parathyroid hormone and calcitonin on renal acid excretion and bicarbonate absorption in normal dogs and to elucidate their role in the development of renal acidosis. Standard clearance studies will be performed on acidotic or bicarbonate loaded animals. Net acid excretion and bicarbonate absorption will be measured before and after alterations in the levels of calcium, parathyroid hormone, calcitonin, vitamin D or cyclic adenosine monophosphate. These studies will be performed on normal dogs and on dogs with unilateral renal disease both in the presence or absence of azotemia. The results of the proposed research will serve to clarify the mechanism of acidosis in renal disease and improve its treatment.